(1) Field of the Invention
The present invention relates to an improved overhead bi-fold door, and in particular to a bi-fold door having a biasing means for initially urging the interface of the door panels outwardly and a latching means that is automatically engaged when closing the door.
(2) Description of the Prior Art
Overhead bi-fold doors, particularly doors of the type used to close large building openings, are generally comprised of upper and lower door panels, with the lower end of the upper panel being hingedly attached to the upper end of the lower panel. The upper edge of the upper panel is hingedly attached to the lintel or header of the door frame. A drive means, generally in the form of a cable that extends from the lower part of the door to an overhead winch is used to raise and lower the door.
The door panels are vertically aligned when in the closed position and in a generally horizontal alignment when the door is open, with the hinged intersection of the door panels extending outwardly. The lower corners of the lower door panel are constrained to move vertically upwardly during opening and closing of the door, generally by attached rollers that extend into tracks along one or both sides of the door frame.
Designers of overhead bi-fold doors face two major challenges. First, since the opening force on the door is vertically upward, and since the door panels are vertically aligned, some provision must be made to initially urge or “kick” the hinged interface of the door panels, i.e., the center of the door, outwardly to enable folding of the doors. Generally, some complex mechanical linkage is used as the biasing mechanism, or a wedge may be positioned between the inner side of the door and the cable so that the cable exerts an outward force against the door.
Second, some locking or latching mechanism must be provided to prevent unauthorized opening of the door when it is closed. Preferably, the latching mechanism is automatically engaged when the door is closed. Generally, the latching mechanism is comprised of a latching arm carried on one of the door panels and a mating latching member mounted on the door frame. Some mechanism, such as a spring or lever is commonly used to move the arm into latching engagement with the latching member as the door is closed.
Neither the biasing means nor the latching mechanisms of prior art overhead bi-fold doors has proven to be entirely satisfactory. Therefore, there is a continuing need for improvements in both aspects.